1. Field of the Invention
The present invention relates to a sheet processing apparatus capable of performing a punch process on a sheet and an image forming system including the sheet processing apparatus.
2. Description of the Related Art
In the related art, there has been proposed a sheet processing apparatus in which sheets respectively having an image formed by an image forming apparatus are conveyed sequentially into an apparatus and a punch process to punch holes can be performed thereon. For example, a sheet processing apparatus on which a punch unit having different number, diameter and position of holes is exchangeably disposed to support a variety of files and rings with a single sheet processing apparatus has been proposed, as disclosed in U.S. Pat. No. 5,746,162.
Further, in the above sheet processing apparatus, punch-processed sheets are eventually discharged to a stack tray while performing a process such as aligning and stapling after being sequentially stacked on a processing tray for temporal stacking by being switched back.
With the sheet processing apparatus proposed in U.S. Pat. No. 5,746,162, when a punch process of a number of holes such as 30 holes is performed, the strength of the sheet end part of the punch-processed side is decreased. Accordingly, when the sheets are stacked on the processing tray and discharged to the stack tray from the processing tray as an ordinary punch process with a few holes such as 2 to 4 holes, there is a fear that following problems occur.
For example, sheets having the punch process of a number of holes performed at the end part thereof are sequentially stacked on the processing tray and alignment is performed by striking the end part of each punch-processed sheet to an abutment member on the processing tray after each sheet is switched back at the sheet tray.
And then, the sheets being aligned at the processing tray are discharged to the stack tray from the processing tray by being pushed by a discharge member movable along the processing tray. At that time, when the sheet is thin, there is a fear that the sheet is buckled as the discharge member pushes out the end part of the punch-processed sheet.
The present invention prevents buckling at an end part of a punch-processed sheet.